Material Specifications & International Equivalents 

As a fundamental low-alloy high-strength steel grade within the GB/T 1591 standard system, Q355B seamless tubes maintain precise correspondence with international standards including:

  • Europe: S355JR (EN standards)

  • Germany: ST52 (DIN standards)

  • United States: A572 Gr.50 (ASTM standards)

  • Japan: SM490YA (JIS standards)

  • UK: S355JR (BS standards)

The designation "Q" represents yield strength in Chinese, "355" indicates minimum yield strength of 355MPa, and "B" denotes quality grade requiring impact testing at 20°C with energy ≥27J, clearly defining its low-alloy high-strength characteristics for cost-effective structural applications.

Mechanical Properties & Performance Characteristics

These high-strength low-alloy tubes demonstrate excellent mechanical capabilities with yield strength ≥355MPa, tensile strength of 470-630MPa, and elongation ≥21% in annealed condition. The enhanced impact toughness ≥27J at room temperature provides reliable performance in various structural applications, representing over 40% strength improvement compared to conventional carbon steels like Q235B while maintaining good plasticity and fracture resistance.

The superior processing characteristics include excellent weldability without complex preheating requirements, strong cold forming capacity for bending, flanging, and stamping operations, and good machinability with tool wear rates comparable to carbon steels. The optimized micro-alloy composition ensures better corrosion resistance through passive film formation and reliable performance in environments down to -20°C.

Technical Advantages: 

  • Optimal balance between high strength and cost-effectiveness

  • Enhanced corrosion and fatigue resistance compared to carbon steels

  • Excellent weldability and cold forming capabilities

  • 30-40% cost reduction versus medium-carbon alloy steels

  • Suitable for mass production and SME manufacturing

  • Reliable performance in structural applications

Applications & Industrial Solutions

Q355B low-alloy seamless tubes serve extensive applications across multiple industrial sectors:

Mechanical Manufacturing 

  • Equipment frames and non-heavy-duty transmission shafts

  • Gear blanks and pressure vessel shells

  • Engineering machinery chassis structural components

  • Machinery applications requiring strength and processability balance

Fluid Transportation Systems 

  • Medium-high pressure water and air pipelines

  • Oil and natural gas transmission pipelines

  • Chemical industry medium-pressure fluid transfer

  • Industrial piping for non-corrosive media up to 10MPa

Automotive & Agricultural Machinery 

  • Commercial vehicle frames and agricultural machinery chassis

  •  Trailer load-bearing structures and automotive bumper skeletons

  • Transportation equipment requiring strength and weight reduction

General Structural Applications

  • Hardware mechanical structural components

  • Large equipment auxiliary structural members

  • Structural applications across various industrial sectors

Customization & Delivery Options 

Q355B tubes are typically supplied in annealed condition (GBK/+A) to optimize cold processing and welding performance. For precision structural components, we provide normalized condition (NBK/+N) to enhance microstructural homogeneity. Precision machining applications can be served with stress-relieved condition (BKS/+SR) to ensure dimensional stability during manufacturing processes.

Tenjan Advantage & Quality Commitment  

Supported by 25 years of specialized experience in low-alloy steel tube manufacturing and comprehensive production capabilities, Tenjan delivers reliable Q355B tubular solutions through advanced quality management systems and technical expertise. Our custom alloy steel capability enables production of various domestic and international steel grades tailored to your specific application requirements, including specialized low-alloy high-strength steels matching global standards like S355JR, ST52, and A572 Gr.50. With full-process manufacturing control and professional technical support, we ensure consistent material quality and performance reliability for your most demanding structural applications. Our flexible order quantities and responsive customer service guarantee seamless project integration and ongoing technical support throughout your operation lifecycle, maintaining our commitment to delivering high-performance low-alloy solutions that exceed customer expectations for strength, durability, and cost efficiency in general structural environments while ensuring global standard compliance.